Merging r225521:

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r225521 | tomatabacu | 2015-01-09 15:00:30 +0000 (Fri, 09 Jan 2015) | 1 line

[mips] Add comment which explains why we need to change the assembler options before and after inline asm blocks. NFC.
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llvm-svn: 232084

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/Mips/MipsAsmPrinter.cpp b/llvm/lib/Target/Mips/MipsAsmPrinter.cpp
index 94b7c0d9807b..fac3f79491b9 100644
--- a/llvm/lib/Target/Mips/MipsAsmPrinter.cpp
+++ b/llvm/lib/Target/Mips/MipsAsmPrinter.cpp
@@ -725,6 +725,12 @@ void MipsAsmPrinter::emitInlineAsmStart(
     const MCSubtargetInfo &StartInfo) const {
   MipsTargetStreamer &TS = getTargetStreamer();
 
+  // GCC's choice of assembler options for inline assembly code ('at', 'macro'
+  // and 'reorder') is different from LLVM's choice for generated code ('noat',
+  // 'nomacro' and 'noreorder').
+  // In order to maintain compatibility with inline assembly code which depends
+  // on GCC's assembler options being used, we have to switch to those options
+  // for the duration of the inline assembly block and then switch back.
   TS.emitDirectiveSetPush();
   TS.emitDirectiveSetAt();
   TS.emitDirectiveSetMacro();